1. Field of the Invention
The present invention relates to a method of manufacturing a polishing pad. More particularly, the present invention relates to a method of manufacturing a polishing pad having grooves thereon.
2. Background of the Invention
In an integrated circuit fabrication, Chemical Mechanical Polishing (CMP) is one of the most important global planarization techniques to remove minute unevenness on a wafer surface to achieve planarization. The technique uses of a grinder-like mechanical polishing theory, so that an uneven surface profile of a wafer can be planarized when an appropriate reagent is used. During a polishing process, the polishing pad moves on the wafer, and the abrasive particles of the reagent pressed by the polishing pad contact with and slide on the wafer, so that the wafer is polished due to the friction between the wafer and the abrasive particles. The softness, the hardness, and the roughness of the physical property of the polishing pad have an effect on the interaction between the abrasive particles in the slurry, so that the interaction becomes irregular in the horizontal direction and the vertical direction. Under a prescribed pressure, a force in the horizontal direction is one of the important factors, which decides the quality of the planarization. The polishing pad must sustain the press of the polishing head of the wafer to maintain the planarization. In addition, the distribution of the abrasive particles in the slurry is very important to the uniformity of the polished surface of the wafer. Accordingly, the polishing pad must have enough hardness to provide the polishing function and have enough cells to hold the slurry.
The polishing pad further has grooves formed thereon. The grooves provide a roughness surface to benefit polishing and advantage the uniformity of the slurry distribution. The larger grooves can promote the fine particles in the slurry to disperse uniformly and can hold much of the removal residue and inactive slurry. However, the polishing presses cannot maintain coincidence if the grooves too large. Accordingly, the planarization of the polished surface is lower.
A method of manufacturing polishing pad in the prior art has been disclosed. A polymer material is injected into a mold. After the polymer is cured and molded, a mold release process is performed to obtain a molding article. Afterwards, the molding article is cut by a lathe or a machining center to form the desired feature of grooves.
In addition, U.S. Pat. Nos. 4,841,680 and 6,095,902 of Rodel Inc. disclose methods of manufacturing polishing pad. The former describes a poromeric polishing pad formed on a first substrate is formed using solvent/non-solvent polymer coagulation technology and high temperature to evaporate the residue solvent. Thereafter, a second substrate is affixed to the top of the poromeric layer, and the first substrate and the poromeric base layer are removed using a blade or a rotating abrasive cylinder to expose and open the underlying cell. The latter describes that the solid ingredients are mixed, melted, and reacted in a mold to form a cake. The cake is then sliced or cut to form polishing layers and then the polishing layer is affixed to a backing or supporting layer to form a polishing pad.
However, in the above methods, the steps of polishing the pad comprise molding, removing the manufacturing substrate/cutting to form layers and bonding. Accordingly, the process requires much time and work. In addition, the processes of removing the manufacturing substrate/cutting to form layers are difficult to control. Therefore, the size of the cells are not uniform, the surface cells are smaller, the opening walls of the working surface increase, and the diameter of surface cell is smaller than the diameter of the underlying cell. Accordingly, the polishing stability is low.
On the other hand, Taiwan Patent Appl. No. 90,123,032 of Rodel Inc in U.S.A. discloses a method of manufacturing a polishing pad having a micro-texture thereon. The micro-texture was created by utilizing an Ikegai, Model AX4ON lathe and a lathe bit made from high-speed tool steel mounted in a standard bit holder. The tool was applied to the pad surface at a cut depth of 0.013 mm and translated in one pass on a linear path across the pad surface along the equator. The speed controller adjusted the rotational speed of the pad to maintain a constant tool velocity relative to the pad (in the azimuthal direction) of 6 meters/min. Cutting debris was removed using a 3.5 HP Sears Craftsman Wet/Dry Vacuum. However, the grooves on the polishing pad are formed by means of cutting, so that the sharp and the linear velocity of the blade, the temperature and the humidity of the atmosphere are not fixed. Accordingly, the numbers of the macro defects formed on the polishing pad are different, and the performances of each polishing pad have a large difference.